Intervertebral cages, in particular for treating degeneration of the spine, are already known. For example, one such cage is described in document EP-A-1 104 662. It essentially comprises a disk-shaped spacer having two substantially plane and parallel opposite base faces and a side wall uniting the two base faces. The spacer is suitable for being placed between the facing faces of two vertebral bodies respectively of two consecutive vertebrae, to replace the damaged disk situated between those two vertebrae, the two base faces of the spacer being placed in contact with the vertebral bodies. The spacer may also have an open cavity in which it is possible to place a bone graft or the like in order to bond together the two vertebral bodies by osteosynthesis. The cage also includes at least one member having two chamfered opposite ends, and means for moving the member relative to a first of two side wall portions so that the member can take up two positions, a first position in which the member is situated entirely within the space lying between the first and second planes containing the two base faces of the spacer, and a second position in which the two opposite ends of the member emerge from either side of said space.
In the above-described cages, the anchor member is associated with a spacer on one of the faces thereof. Such an embodiment requires a certain number of elements in order to make it relatively easy to turn the member relative to the spacer. In an attempt to minimize the number of such elements, a solution has been tried that consists in positioning the anchor member substantially in the middle portion of the spacer, as for example in the embodiment described in WO 01/01894. The solution adopted for making that cage has nevertheless not given full satisfaction, essentially because the way the member is integrated in the middle portion of the spacer is still too complex and makes it relatively complicated to implant the cage between two vertebrae.
In an attempt to mitigate the above-mentioned drawbacks, an intervertebral cage has also been made as described, for example, in U.S. Pat. No. 6,371,987 B1. That cage satisfies in general manner the requirements of practitioners, but it still presents drawbacks, in particular for its manufacture.